1. Field of the Invention
The apparatuses and methods consistent with the present invention relate to an organic electroluminescent device (OELD), and a method of manufacturing the OELD, and more particularly, to an OELD that has increased luminance efficiency and lifetime, and a method of manufacturing the OELD.
2. Description of the Related Art
An OELD is a display device that displays images using light emitted from an organic light emitting layer by a combination of holes, supplied from an anode electrode, and electrons, supplied from a cathode electrode, in the organic light emitting layer formed between the anode electrode and the cathode electrode. Due to the excellent display characteristics of the OELD, such as a large viewing angle, high speed response, thinness, low manufacturing costs, and high contrast, the OELD is expected to become one of the next generation flat panel display devices.
FIG. 1 is a cross-sectional view illustrating a related art OELD. Referring to FIG. 1, an anode electrode 12 is formed on a transparent substrate 10 using a transparent conductive material such as indium tin oxide (ITO). An organic light emitting layer 14 is formed on the anode electrode 12 using an organic material, and a cathode electrode 16 is formed on the organic light emitting layer 14 using a metal. In the above structure, when a predetermined voltage is applied between the anode electrode 12 and the cathode electrode 16, visible light is emitted from the organic light emitting layer 14, and visible light displays an image by emitting externally through the anode electrode 12 and the transparent substrate 10. However, in the OELD having the above mentioned structure, a portion of visible light emitted from the organic light emitting layer 14 is not able to pass through interfaces between layers and is lost since the transparent substrate 10, the anode electrode 12, the organic light emitting layer 14, and the cathode electrode 16 having different refractive indexes from each other are stacked in a planar structure. More specifically, there is a drawback in that approximately 40% of visible light emitted from the organic light emitting layer 14 is lost at an interface between the organic light emitting layer 14 and the anode electrode 12 due to a total reflection at the interface, and another 40% of visible light is absorbed by the cathode electrode 16 and absorbed as heat due to a surface plasmon resonance (SPR) phenomenon occurring at a flat interface between the organic light emitting layer 14 and the cathode electrode 16, which is formed of a metal.